FIELD OF INVENTION
The present invention relates to locating of steam turbine lock blades of various
sizes and rhomboidal angles during root and shroud machining on CNC horizontal
machining center.
More particularly, the present invention relates to development of universal
adjustment device for locating steam turbine lock blades along their central axis
for carrying out root and shroud milling on CNC horizontal machining center.
BACKGROUND OF THE INVENTION:
Steam turbines blade is a very precise and critical component in a steam turbine
system. Each stage of steam turbine blades which are fitted into the turbine
rotor, consist of a number of regular blades with slots in the root as well as 2 no.
of special 'lock' blades which do not have slots cut into them.
Root and shroud milling of steam turbine blades is carried by using two adjacent
planes in the blade root and shroud as well as the root slot to completely define
the position of the blade in the fixture on a horizontal milling machine.
The fixture which is used to carry out root and shroud milling is a specially
designed one, in which two adjacent planes of the blade are used as reference to
locate the blade in two axes and the slot of the blade is used to locate the blade
position along the final third axis. After the blade position has been fixed, the
fixture clamps the blade on the root and shroud from four sides, holding it
securely for machining of root and shroud end surfaces. This operation is also
known as root and shroud milling.

In this system, for the lock blades however, due to absence of any slot in the
root it is not possible to fix accurately the blade location along the blade's central
axis. The lock blades are positioned in the fixture on the basis of operator's
estimation and through a method of trial and error. This results in longer cycle
times of manufacturing as compared to normal blades as setting the blades in
the fixture takes extra time. Also there is a significant chance of the blade being
rejected due to incorrect positioning.
As there are a number of stages in a single steam turbine rotor and in a shop
manufacturing a large number of rotor annually, the rework/ rejection in the
manufacture of these lock blades is cumbersome, time consuming and increases
the possibility of error.
OBJECT OF THE INVENTION
It is therefore the object of the present invention to provide a universal
adjustable device for locating steam turbine lock blades along their central axis
for carrying out root and shroud milling on CNC horizontal machining center.
Another object of the invention is to reduce the rejection of steam turbine lock
blade during root and shroud milling operation.
Further object of the invention is to shorten the setting time required for root
and shroud milling of steam turbine lock blades.
A still further object of the invention is to improve the productivity of root and
shroud milling of steam turbine lock blades.

SUMMARY OF THE INVENTION
Accordingly, there is provided a universal adjustable device (A) in fig 2 for
locating steam turbine blade along their central axis for carrying out their root
and shroud milling on CNC horizontal machining center comprising mainly of:-
a) Body (1)
b) Rod (2)
c) Shunt (3)
d) Locating Rod (4)
e) Locking Bolt (5)
The body (1) fits onto the fixture body on the horizontal milling machine. Two
no. of Locking Bolts (5) are used to tighten the Body (1) securely on the fixture.
The rod (2) is screwed on to the body (1) in the threaded hole on the body (1).
The shunt (3) slips on the rod (2) and both the shunt (3) and rod (4) are locked
rigidly using a locking bolt (5) at the desired position. The locating rod (4) slides
through the shunt (3) and can be adjusted before being locked using a locking
bolt (5).
In case of a stream turbine lock blade, after reference has been taken from two
adjacent planes of the root and shroud, and the blade has been fixed in 2
directions, the tip of the locating Rod (4), which is in the form of a sphere can be
used to define a point along the 3rd axis, at the blade surface at the root and
profile junction for the complete fixing of the blade position in the fixture.
As the position of the shunt (3) and the locating rod (4) are adjustable, it is
possible to define the locating point for different types of stream turbine lock
blades. As the only difference between a normal steam turbine blade and its lock
variant is the absence of slots in the root, it is possible to define the locating
point for a normal stream turbine blade (as its position is already defined firmly

using 2 adjacent planes and the slot). The device can be locked, fixing it in
position. Then the lock blade can be put into the fixture and its position be
defined using its 2 adjacent planes and the point given by the device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1(a) (sheet no.l) shows the 3d model of universal adjustable device for
locating steam turbine lock blade along their central axis for carrying out their
root and shroud milling on CNC horizontal machining center according to present
invention in its right hand configuration. Fig. 1(b) (sheet no. 1) shows the 3d
model in the left hand configuration.
Fig. 2 (sheet no. 2) shows the sketch of the universal adjustable device with all
components marked.
Fig. 3 (sheet no. 3) shows the exploded view of the assembly of the universal
adjustable device.
Fig. 4 (sheet no. 4) shows the sketch of the locating rod (4) which has a sphere
at one end which is used for defining the locating point for the steam turbine
lock blade.
Fig. 5(a) (sheet no. 5) shows a regular steam turbine blade along with the planes
which are used to fix the blade's position in the fixture along with the blade slot
which is used to fix the blade's position along its central axis. Fig. 5(b) (sheet
no.5) shows a regular steam turbine blade placed in the fixture for horizontal
milling machine where it is evident that the slot in the root fixes the position of
the blade along its central axis via a locator which goes into the slot.

Fig. 6(a) (sheet no.6) shows a steam turbine Nock' blade which has no root slot
and hence its position cannot be fixed accurately along the blade axis. Fig. 6 (b)
(sheet no. 6) shows a 'lock' steam turbine blade placed in the fixture for
horizontal milling machine where it is evident that the absence of a slot in the
root does not allow the position of the blade to be defined along its central axis.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE
PRESENT INVENTION:
Fig. 1, Fig. 2 and Fig. 3 (sheet no. 1, 2 and 3) show the universal adjustment
device comprising a body (1), a rod (2), a shunt (3), locating rod (4) and bolts
(5).
The Rod (2) is screwed on to the body (1) on the right or left side depending on
the hand of the blade to be located.
Now the device is fixed onto the fixture for root and shroud milling on horizontal
milling machine as shown in Figure 5(b) and 6(b). The locking bolts (5) are used
to clamp the body (1) onto the fixture.
The shunt (3) slip on the rod (3) and its position is locked at the required place
using a locking bolt (5). The locating rod (4) passes through the shunt (3) and is
locked at the required position using a locking belt (5).
A regular steam turbine blade can be easily fixed in the fixture for root and
shroud milling because of its root a lot which allows for locating the blade in the
fixture along its axis as shown in Fig. 5(b). The corresponding Nock' steam
turbine blade on the other hand has no such slot and thus its position cannot be

fixed accurately along the blade axis in the fixture for the root and shroud milling
as.shown in Fig. 6(b).
The assembled device can be fixed onto the fixture for carrying out root and
shroud milling. When a regular steam turbine blade is fully fixed in the fixture the
device can be used to locate a point at the plannar junction for the blade root
which fixes the blade position along its central axis.
When the corresponding 'lock' steam turbine blade needs to be fixed in the
fixture for carrying out root and shroud milling, the point which was located by
the device previously can be used to define the blade position in the fixture
before clamping.
Since the shunt (3) and the locating rod (4) are fully adjustable, it is possible to
locate fixing points for a wide range of steam turbine lock blades for carrying out
root and shroud milling on a horizontal milling machine.

WE CLAIM
1. A universal adjustable device (A) for locating steam turbine lock blades along
the central axis for carrying out root and shroud milling on CNC horizontal
machining centre comprising:
body (01) having plurality of holes with internal thread;
rod (02) having one end threaded that fits into body (01) by thread connection
in perpendicular position;
a shunt (03) with plurality of plain holes and threaded holes where the shunt
(03) can slide through rod (02), the shunt (03) can also rotate around the axis of
rod (04) which can slide inside the other hole of shunt (03) and locked by bolt
(5) at any particular position; a rod (04) having one end with plain face and the
other end with spherical round surface used for locating the blade surface, slide
through the hole provided in the shunt (03) characterized in that the fixing
mechanism comprising shunt (03), rod (02) and rod (04) can give a three
dimensional movement to the spherical end for locating the lock blade surface.
2. The device (A) as claimed in claim 1, where the individual components are
hardened.
3. The device (A) as claimed in claim 1 which can be fixed on to the fixture for
root shroud milling on milling machine.
4. A method for locating steam turbine lock blade along the central axis for root
and shroud milling comprising:
- loading the regular steam turbine blade with slot in the fixture and locating its
position using two adjacent planes and the blade slot which is used to fix the
blades position along its central axis
- locating the blade surface at the root and profile junction by the spherical end
of .the device to define a point along the 3rd axis

- locking the device securely onto the fixture with the defined point firmly in
place at this time which indicates that the position of the point is defined with
respect to two adjacent planes and the slot
- taking out the regular blade and loading the lock blade into the fixture
- locating the correct position of the lock blade using two adjacent planes and
the point defined by the device and clamping the lock blade for carrying out root
and shroud machining.